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//===-- llvm/CodeGen/LiveInterval.h - Interval representation ---*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// This file implements the LiveRange and LiveInterval classes. Given some
// numbering of each the machine instructions an interval [i, j) is said to be a
// live interval for register v if there is no instruction with number j' > j
// such that v is live at j' and there is no instruction with number i' < i such
// that v is live at i'. In this implementation intervals can have holes,
// i.e. an interval might look like [1,20), [50,65), [1000,1001). Each
// individual range is represented as an instance of LiveRange, and the whole
// interval is represented as an instance of LiveInterval.
#include <iosfwd>
#include <vector>
#include <cassert>
namespace llvm {
class MRegisterInfo;
/// LiveRange structure - This represents a simple register range in the
/// program, with an inclusive start point and an exclusive end point.
/// These ranges are rendered as [start,end).
struct LiveRange {
unsigned start; // Start point of the interval (inclusive)
unsigned end; // End point of the interval (exclusive)
unsigned ValId; // identifier for the value contained in this interval.
LiveRange(unsigned S, unsigned E, unsigned V) : start(S), end(E), ValId(V) {
assert(S < E && "Cannot create empty or backwards range");
/// contains - Return true if the index is covered by this range.
bool contains(unsigned I) const {
return start <= I && I < end;
bool operator<(const LiveRange &LR) const {
return start < LR.start || (start == LR.start && end < LR.end);
bool operator==(const LiveRange &LR) const {
return start == LR.start && end == LR.end;
void dump() const;
LiveRange(); // DO NOT IMPLEMENT
std::ostream& operator<<(std::ostream& os, const LiveRange &LR);
inline bool operator<(unsigned V, const LiveRange &LR) {
return V < LR.start;
/// LiveInterval - This class represents some number of live ranges for a
/// register or value. This class also contains a bit of register allocator
/// state.
struct LiveInterval {
typedef std::vector<LiveRange> Ranges;
unsigned reg; // the register of this interval
float weight; // weight of this interval
Ranges ranges; // the ranges in which this register is live
LiveInterval(unsigned Reg, float Weight)
: reg(Reg), weight(Weight), NumValues(0) {
typedef Ranges::iterator iterator;
iterator begin() { return ranges.begin(); }
iterator end() { return ranges.end(); }
typedef Ranges::const_iterator const_iterator;
const_iterator begin() const { return ranges.begin(); }
const_iterator end() const { return ranges.end(); }
/// advanceTo - Advance the specified iterator to point to the LiveRange
/// containing the specified position, or end() if the position is past the
/// end of the interval. If no LiveRange contains this position, but the
/// position is in a hole, this method returns an iterator pointing the the
/// LiveRange immediately after the hole.
iterator advanceTo(iterator I, unsigned Pos) {
if (Pos >= endNumber())
return end();
while (I->end <= Pos) ++I;
return I;
void swap(LiveInterval& other) {
std::swap(reg, other.reg);
std::swap(weight, other.weight);
std::swap(NumValues, other.NumValues);
bool containsOneValue() const { return NumValues == 1; }
unsigned getNextValue() {
return NumValues++;
bool empty() const { return ranges.empty(); }
/// beginNumber - Return the lowest numbered slot covered by interval.
unsigned beginNumber() const {
assert(!empty() && "empty interval for register");
return ranges.front().start;
/// endNumber - return the maximum point of the interval of the whole,
/// exclusive.
unsigned endNumber() const {
assert(!empty() && "empty interval for register");
return ranges.back().end;
bool expiredAt(unsigned index) const {
return index >= endNumber();
bool liveAt(unsigned index) const;
/// getLiveRangeContaining - Return the live range that contains the
/// specified index, or null if there is none.
const LiveRange *getLiveRangeContaining(unsigned Idx) const;
/// joinable - Two intervals are joinable if the either don't overlap at all
/// or if the destination of the copy is a single assignment value, and it
/// only overlaps with one value in the source interval.
bool joinable(const LiveInterval& other, unsigned CopyIdx) const;
/// getOverlapingRanges - Given another live interval which is defined as a
/// copy from this one, return a list of all of the live ranges where the
/// two overlap and have different value numbers.
void getOverlapingRanges(const LiveInterval &Other, unsigned CopyIdx,
std::vector<LiveRange*> &Ranges);
/// overlaps - Return true if the intersection of the two live intervals is
/// not empty.
bool overlaps(const LiveInterval& other) const {
return overlapsFrom(other, other.begin());
/// overlapsFrom - Return true if the intersection of the two live intervals
/// is not empty. The specified iterator is a hint that we can begin
/// scanning the Other interval starting at I.
bool overlapsFrom(const LiveInterval& other, const_iterator I) const;
/// addRange - Add the specified LiveRange to this interval, merging
/// intervals as appropriate. This returns an iterator to the inserted live
/// range (which may have grown since it was inserted.
void addRange(LiveRange LR) {
addRangeFrom(LR, ranges.begin());
/// join - Join two live intervals (this, and other) together. This
/// operation is the result of a copy instruction in the source program,
/// that occurs at index 'CopyIdx' that copies from 'other' to 'this'. This
/// destroys 'other'.
void join(LiveInterval& other, unsigned CopyIdx);
/// removeRange - Remove the specified range from this interval. Note that
/// the range must already be in this interval in its entirety.
void removeRange(unsigned Start, unsigned End);
bool operator<(const LiveInterval& other) const {
return beginNumber() < other.beginNumber();
void print(std::ostream &OS, const MRegisterInfo *MRI = 0) const;
void dump() const;
unsigned NumValues; // the number of distinct values in this interval.
Ranges::iterator addRangeFrom(LiveRange LR, Ranges::iterator From);
void extendIntervalEndTo(Ranges::iterator I, unsigned NewEnd);
Ranges::iterator extendIntervalStartTo(Ranges::iterator I, unsigned NewStr);
LiveInterval& operator=(const LiveInterval& rhs); // DO NOT IMPLEMENT
inline std::ostream &operator<<(std::ostream &OS, const LiveInterval &LI) {
return OS;